1. Field of the Invention
The present invention relates to a lens-fitted photographic film unit, wherein a unit body containing a roll of photographic film has a taking lens and an exposure mechanism incorporated therein and is encased in an outer case which is formed by folding a sheet material.
2. Background Art
Lens-fitted photographic film units, hereinafter referred to as film units, have been known as a kind of single-use preloaded camera which is affordable for everyone and permits enjoying photography with ease.
In view of the above use, the film units must not be expensive. To make the appearance attractive at a low cost, the body of the film unit is wrapped or encased in an outer case having an ornamental pattern printed thereon. The ornamental pattern further serves to distinguish the film unit from other types of film units. The outer case also has information about the film unit such as the type of the preloaded photographic film, the type of the taking lens, the format of the picture frame, and instructions how to use the film unit. Moreover, the outer case prevents dust from setting on the unit body or entering inside the unit body. The outer cases are mostly made of cardboard and are formed by folding and sticking a blanked sheet of cardboard into a box.
However, due to resiliency of the cardboard, the folded portions of the outer case have a tendency to unfold so the outer case tends to bulge or swell, especially when it has open sides or many or large openings. In case being made of cardboard, the outer case may expands and swell out due to moisture-absorption.
The bulged outer case spoils the appearance of the film unit, and cannot sufficiently protect the unit body from dust. Where the outer case covers some operational members of the film unit such as a flash charge button or a grip, the loosened or swelled outer case can impair smoothness in operation.
To solve the above problem, a rectangular outer case of the film unit has been suggested in JPB 6-6348, of which a front side is formed as an outwardly concave and inwardly convex surface so that the front wall and thus rear wall are kept in contact with the unit housing even when the outer case is somewhat unfolded or loosened. To form the curved surface in one side of the outer case, the cardboard is folded along a pair of curved lines which define opposite margins of the curved surface.
However, it is difficult to fold along the curved lines and to form thereafter a substantially rectangular box. A complicated and accurate assembling machine is needed for automatic forming of such outer cases having curved sides.
There have been suggested film units having a grip portion which protrudes forward from the front surface of the unit body. Because of the difference in thickness between the grip and the front surface, the outer case of such a film unit tends to lose contact with the border portion between the front surface and the grip, which will make holding of the film unit unsteady.